Wireless networks have experienced increased development in the past decade. One of the most rapidly developing areas is mobile ad-hoc networks. Physically, a mobile ad-hoc network includes a number of geographically-distributed, potentially mobile nodes sharing a common radio channel. Compared with other types of networks, such as cellular networks or satellite networks, the most distinctive feature of mobile ad-hoc networks is the lack of any fixed infrastructure. The network may be formed of mobile nodes only, and a network is created “on the fly” as the nodes come close enough to transmit with each other. The network does not depend on a particular node and dynamically adjusts as some nodes join or others leave the network.
Because of these unique characteristics, routing protocols for governing data flow within ad-hoc networks are required which can adapt to frequent topology changes. Two basic categories of ad-hoc routing protocols have emerged in recent years, namely reactive or “on-demand” protocols, and proactive or table-driven protocols. Reactive protocols collect routing information when a particular route is required to a destination in response to a route request. Examples of reactive protocols include ad-hoc on demand distance vector (AODV) routing, dynamic source routing (DSR), and the temporally ordered routing algorithm (TORA).
On the other hand, proactive routing protocols attempt to maintain consistent, up-to-date routing information from each node to every other node in the network. Such protocols typically require each node to maintain one or more tables to store routing information, and they respond to changes in network topology by propagating updates throughout the network to maintain a consistent view of the network. Examples of such proactive routing protocols include destination-sequenced distance-vector (DSDV) routing, which is disclosed in U.S. Pat. No. 5,412,654 to Perkins; the wireless routing protocol (WRP); and clusterhead gateway switch routing (CGSR). A hybrid protocol which uses both proactive and reactive approaches is the zone routing protocol (ZRP), which is disclosed in U.S. Pat. No. 6,304,556 to Haas.
One challenge to the advancement of ad-hoc network development is that of security. More particularly, since nodes in a mobile ad-hoc network all communicate wirelessly, there is a much greater risk of eavesdropping or data compromise by unauthorized users. Because of the early stage of development of ad-hoc networks and the numerous other challenges these networks present, the above routing protocols have heretofore primarily focused solely on the mechanics of data routing and not on security.
Some approaches are now being developed for providing more secure data transmissions within mobile ad-hoc networks. One such approach is outlined in a Capstone Proceeding paper by Nguyen et al. entitled “Security Routing Analysis for Mobile Ad Hoc Networks,” Department of Interdisciplinary Telecommunications, University Of Colorado at Boulder, Spring 2000. In this paper, the authors suggest using the U.S. Data Encryption Standard (DES) for encrypting plain text messages. To authenticate the messages, digital signatures and keyed one-way hashing functions with windowed sequence numbers are proposed. More particularly, public-key encryption is used along with a one-way hash function to provide the digital signature. The sender uses the one-way hash function on the message and then encrypts the hash value with their private key. The message, along with the encrypted hash value, is sent to its destination. At the receiver, the hash value is also calculated based upon the message and is compared with the received hash value that was decrypted with the sender's public key. If they are the same, then the signature is authenticated.
While the above approach may provide some measure of enhanced security, one potential drawback is that the private key may be discoverable by external attack. That is, a third party may potentially be able to discover information about the private key by collecting and comparing messages from the sender. By knowing the private key, a third party may then be able to impersonate the sender and cause significant disruption to network operation, for example.